Gamma rays are electromagnetic waves with no mass and no charge, thus they interact least with matter and have the highest penetrating power. Alpha particles (He nuclei) are stopped by paper. Beta particles (electrons) can be stopped by aluminum. Gamma requires thick lead or concrete.
Explanation:
Autocatalysis occurs when one of the products of a chemical reaction acts as a catalyst for that same reaction. As the reaction proceeds and the product accumulates, the rate of the reaction increases. A classic example is the oxidation of oxalic acid by potassium permanganate, where the Mn2+ ions produced catalyze the reaction.
Explanation:
Fraction remaining = (1/2)^n = 1/16 => n = 4 half-lives. Time = n × half-life = 4 × 4 = 16 years. After 1 half-life: 1/2, 2: 1/4, 3: 1/8, 4: 1/16. Radioactive decay is exponential. So after 16 years, only 1/16th of original radioactive atoms remain.
Explanation:
Naphthalene sublimes on heating, directly changing to vapor, while sand remains. The naphthalene vapor can be condensed on a cold surface. This technique works for any mixture where one component sublimes (naphthalene, camphor, NH₄Cl). Filtration works for insoluble solids in liquids. Magnetic separation for magnetic ores. Distillation for liquid mixtures.
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